This disclosure relates generally to techniques for performing wellsite operations. More specifically, the disclosure relates to techniques for measuring downhole parameters, such as weight on bit (WOB).
In the oil and gas exploration and production industry, subsurface formations are accessed by drilling wellbores from the surface. A drill bit is mounted on the lower end of a tubular string of pipe (referred to as a “drill string”), and advanced into the earth from the surface to form a wellbore. A bottom hole assembly (BHA) is provided along the drill string to perform various downhole operations, such as providing power to the drill bit to drill the wellbore and performing downhole measurements. Drilling fluid or “mud” may be pumped down through the drill string from the surface, and exited through nozzles in the drill bit. The drilling fluid may carry drill cuttings out of the wellbore, and back up to the surface through an annulus between the drill string and the wellbore wall.
During or after drilling, the drill string may be removed and other downhole tools, such as testing, perforating, injection, production and other tools and/or tubing may be positioned in the well to perform downhole operations. During such downhole operations, it may be desirable to measure downhole parameters, such as forces acting on the downhole tool and/or bit, downhole pressures (internal and/or external), torque on bit (TOB), weight on bit (WOB), etc. WOB refers to weight that is applied to the bit, for example, from the BHA and/or surface equipment.
Measurement of downhole parameters, such as WOB, may be useful in performing downhole operations. WOB may be used, for example, to steer drilling and/or to adjust drilling rates, bit penetration, bit wear, etc. Examples of various techniques for measuring downhole parameters, such as WOB, are provided in U.S. Pat. Nos. 6,802,215 and 6,957,575.